Acute apical periodontitis refers to the acute inflammation of the tooth root and its surrounding tissues, including the cementum, periodontal ligament, and alveolar bone. It often develops from acute pulpitis or represents an acute exacerbation of chronic apical periodontitis. Clinically, it can be categorized into two types: acute serous apical periodontitis and acute suppurative apical periodontitis. The treatment principles for acute apical periodontitis involve establishing drainage, controlling inflammation, alleviating pain, and preserving the affected tooth. Once the acute inflammation is under control, root canal treatment should be performed on the affected tooth. If the tooth cannot be preserved, timely extraction is recommended. During the acute phase, antibiotics such as metronidazole, amoxicillin, and cephalosporins, as well as analgesics like diclofenac sodium and ibuprofen, may be appropriately administered. The prognosis for acute apical periodontitis is generally good with active treatment; however, if systemic symptoms such as weight loss, anemia, and chronic toxic consumption occur, the prognosis may be poor.